There is a catalyst support for exhaust gas purification supporting a catalyst for purifying problematic gas components such as HC (hydrocarbons), CO (carbon monoxide), and NOx (nitrogen compounds), which are harmful to the human body when released to the air.
A catalytic converter supporting a catalyst, which is used for exhaust gas purification of automobiles and motorcycles, is provided on the exhaust gas passage for the purpose of purifying exhaust gas of an internal combustion engine. For example, in urea SCR (Selective Catalytic Reduction), the urea water injected on the inlet side of an SCR reactor is hydrolyzed with the heat of the exhaust gas to produce ammonia, and NOx (nitrogen compounds) in the exhaust gas and ammonia are subjected to reduction reaction with the SCR catalyst in the SCR reactor to produce harmless nitrogen and water, and the above-mentioned catalytic converter is used as the SCR reactor. In a similar way, a substrate supporting a catalyst is also used in a methanol reformer that reforms hydrocarbon compounds such as methanol with steam to generate hydrogen-rich gas, a CO remover that reforms CO to CO2 to remove CO, or an H2 combustion apparatus that burns H2 to H2O and removes H2.
These catalyst supports are configured by partially bonding a honeycomb body formed by winding metal-made flat foil and corrugated foil, and an outer cylinder covering the outer peripheral surface in the radial direction of the honeycomb body. A large number of exhaust gas flow paths extending in the axial direction are formed in the honeycomb body, and exhaust gas can be purified by flowing the exhaust gas from the inlet side end face of the honeycomb body to the outlet side end face inside the exhaust gas flow paths.
When the catalyst falls off from the support, the purification function of the catalytic converter is reduced, so that the substrate and the catalyst are required to firmly adhere. Patent Literature 1 discloses a catalytic converter including a honeycomb metal foil, an oxide film formed on a surface of the metal foil, an adhesive layer (ceramic layer) formed on a surface of the oxide film, and a zeolite layer held in an adhesive layer.
In the invention disclosed in Patent Literature 1, the problem to be solved is that the oxide film and the zeolite layer have very different properties and structures and strong adhesion cannot be obtained even when the zeolite layer is formed directly on the oxide film, and the separation of the zeolite is prevented by interposing an adhesive layer between the oxide film and the zeolite layer.
Patent Literature 1 also discloses that the average surface roughness of the oxide film is 2 to 4 μm and the average height from peaks to valleys is at least 0.2 μm.
Patent Literature 2 discloses a material for a catalyst support for exhaust gas purifier using a ferritic stainless steel foil that has a composition containing, by mass %, C: 0.050% or less, Si: 0.20% or less, Mn: 0.20% or less, P: 0.050% or less, S: 0.0050% or less, Cr: 10.5% or more and 20.0% or less, Ni: 0.01% or more and 1.00% or less, Al: more than 1.5% and less than 3.0%, Cu: 0.01% or more and 1.00% or less, and N: 0.10% or less, and further containing at least one or two or more selected from Ti: 0.01% or more and 1.00% or less, Zr: 0.01% or more and 0.20% or less, and Hf: 0.01% or more and 0.20% or less, with the balance being Fe and unavoidable impurities, and has a composite film of an Al oxide film and a Cr oxide film on the surface thereof.